Traditionally, pushrim propulsion has been used in powering a wheelchair. Pushrims are provided adjacent to the main wheels of the wheelchair, allowing a user to apply force to the pushrims in order to move the wheelchair forwardly or rearwardly. A concern with the use of pushrim propulsion is that the poor human-to-chair biomechanics result in efficiencies and sometimes injury. Users of pushrim wheelchairs may suffer from Repetitive Strain Injuries (RSI) of the wrists and shoulders.
Another approach for manual wheelchairs is the use of levers which are “rowed.” It has been shown that lever propulsion avoids the ergonomic and inefficiency shortcomings of the pushrim approach.
Often, the two main wheels of a wheelchair are connected to the wheelchair frame by quick-release mechanisms. This allows the wheels to be removed for purposes of storage or transportation. Additionally, when advancements occur in the design of wheelchair propulsion, the use of quick-release mechanisms readily allow “upgrades” to existing wheelchair frames. However, a difficulty is that wheelchair frames have various geometries, so that an attachment assembly for an upgrade may be suitable for only a limited number of possible wheelchair frames. A second possible problem is that the attachment of a lever propulsion system to a wheelchair frame must withstand significant torque that is generated during rowing of a lever.
U.S. Pat. No. 5,020,815 to Harris et al. describes a retrofitable attachment for converting conventional wheelchairs into steerable self-propelled wheelchairs. Various connections are made to the wheelchair, including connections to the front caster wheels in order to provide the steering capability. While the system described in Harris et al. operates well for its intended purpose, the attachment requirements are significant and the chair loses its quick-release feature for removing the drive wheels.
U.S. Patent Publication No. 2008/0073869 to Patterson describes a lever propulsion system which may be attached to a wheelchair that maintains its quick-release capability. The assembly is connected to the seat tube of the wheelchair frame by a clamp.
It would be beneficial to provide an attachment approach which accommodates retrofit to a greater variety of different wheelchair designs, while still allowing the quick-release capability for removing the two main drive wheels.